Abstract
Multistage fatigue tests were conducted on the single-edge-notch tension specimens of Ni-based superalloy GH4169. Fatigue crack growth data at different stages were recorded with the surface replica technique. Continuum damage mechanics incorporating critical distance theory was used to evaluate fatigue crack initiation life. Then, small and long fatigue crack grow rates were modeled using Shyam’s model and modified Paris law, respectively. Finally, the multistage fatigue model deriving from the above theories was proposed to predict total fatigue life of GH4169. Fatigue life prediction results show that the proposed multistage fatigue model has high accuracy for GH4169.
Highlights
The nickel-based superalloy GH4169 has microstructure and mechanical behaviors similar to Inconel 718
The results show that fatigue cracks initiated from the grain boundaries or surface inclusions.[6]
The results show that the proposed approaches have high accuracy to evaluate fatigue initiation life for GH4169
Summary
The nickel-based superalloy GH4169 has microstructure and mechanical behaviors similar to Inconel 718. The typical models proposed to describe small fatigue crack growth rates include Hobson’s model,[12] Miller’s model,[13] Navarro–Rios’ model,[14] and Shyam’s model.[15] The last stage of fatigue failure process is considered as the long crack growth period This portion is an important part of damage tolerance design and can be described with classical fracture mechanics. Under uniaxial tension loading condition, equation (3) can be changed into the following form[20]
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